In computing, a code page is a character encoding and as such it is a specific association of a set of printable characters and control characters with unique numbers. Typically each number represents the binary value in a single byte. (In some contexts these terms are used more precisely; see Character encoding § Terminology.)
The term "code page" originated from IBM's EBCDIC-based mainframe systems, [1] but Microsoft, SAP, [2] and Oracle Corporation [3] are among the vendors that use this term. The majority of vendors identify their own character sets by a name. In the case when there is a plethora of character sets (like in IBM), identifying character sets through a number is a convenient way to distinguish them. Originally, the code page numbers referred to the page numbers in the IBM standard character set manual, [4] [5] [6] a condition which has not held for a long time. Vendors that use a code page system allocate their own code page number to a character encoding, even if it is better known by another name; for example, UTF-8 has been assigned page numbers 1208 at IBM, 65001 at Microsoft, and 4110 at SAP.
Hewlett-Packard uses a similar concept in its HP-UX operating system and its Printer Command Language [7] (PCL) protocol for printers (either for HP printers or not). The terminology, however, is different: What others call a character set, HP calls a symbol set, and what IBM or Microsoft call a code page, HP calls a symbol set code. HP developed a series of symbol sets, [8] [9] each with an associated symbol set code, to encode both its own character sets and other vendors’ character sets.
The multitude of character sets leads many vendors to recommend Unicode.
IBM introduced the concept of systematically assigning a small, but globally unique, 16 bit number to each character encoding that a computer system or collection of computer systems might encounter. The IBM origin of the numbering scheme is reflected in the fact that the smallest (first) numbers are assigned to variations of IBM's EBCDIC encoding and slightly larger numbers refer to variations of IBM's extended ASCII encoding as used in its PC hardware.
With the release of PC DOS version 3.3 (and the near identical MS-DOS 3.3) IBM introduced the code page numbering system to regular PC users, as the code page numbers (and the phrase "code page") were used in new commands to allow the character encoding used by all parts of the OS to be set in a systematic way. [10]
After IBM and Microsoft ceased to cooperate in the 1990s, the two companies have maintained the list of assigned code page numbers independently from each other, resulting in some conflicting assignments. At least one third-party vendor (Oracle) also has its own different list of numeric assignments. [3] IBM's current assignments are listed in their CCSID repository, while Microsoft's assignments are documented within the MSDN. [11] Additionally, a list of the names and approximate IANA (Internet Assigned Numbers Authority) abbreviations for the installed code pages on any given Windows machine can be found in the Registry on that machine (this information is used by Microsoft programs such as Internet Explorer).
Most well-known code pages, excluding those for the CJK languages and Vietnamese, fit all their code-points into eight bits and do not involve anything more than mapping each code-point to a single character; furthermore, techniques such as combining characters, complex scripts, etc., are not involved.
The text mode of standard (VGA-compatible) PC graphics hardware is built around using an 8-bit code page, though it is possible to use two at once with some color depth sacrifice, and up to eight may be stored in the display adapter for easy switching. [12] There was a selection of third-party code page fonts that could be loaded into such hardware. However, it is now commonplace for operating system vendors to provide their own character encoding and rendering systems that run in a graphics mode and bypass this hardware limitation entirely. However the system of referring to character encodings by a code page number remains applicable, as an efficient alternative to string identifiers such as those specified by the IETF and IANA for use in various protocols such as e-mail and web pages.
The majority of code pages in current use are supersets of ASCII, a 7-bit code representing 128 control codes and printable characters. In the distant past, 8-bit implementations of the ASCII code set the top bit to zero or used it as a parity bit in network data transmissions. When the top bit was made available for representing character data, a total of 256 characters and control codes could be represented. Most vendors (including IBM) used this extended range to encode characters used by various languages and graphical elements that allowed the imitation of primitive graphics on text-only output devices. No formal standard existed for these "extended ASCII character sets" and vendors referred to the variants as code pages, as IBM had always done for variants of EBCDIC encodings.
Unicode is an effort to include all characters from all currently and historically used human languages into single character enumeration (effectively one large single code page), removing the need to distinguish between different code pages when handling digitally stored text. Unicode tries to retain backwards compatibility with many legacy code pages, copying some code pages 1:1 in the design process. An explicit design goal of Unicode was to allow round-trip conversion between all common legacy code pages, although this goal has not always been achieved. Some vendors, namely IBM and Microsoft, have anachronistically assigned code page numbers to Unicode encodings. This convention allows code page numbers to be used as metadata to identify the correct decoding algorithm when encountering binary stored data.
These code pages are used by IBM in its EBCDIC character sets for mainframe computers. [13]
These code pages are used by IBM in its PC DOS operating system. These code pages were originally embedded directly in the text mode hardware of the graphic adapters used with the IBM PC and its clones, including the original MDA and CGA adapters whose character sets could only be changed by physically replacing a ROM chip that contained the font. The interface of those adapters (emulated by all later adapters such as VGA) was typically limited to single byte character sets with only 256 characters in each font/encoding (although VGA added partial support for slightly larger character sets).
When dealing with older hardware, protocols and file formats, it is often necessary to support these code pages, but newer encoding systems, in particular Unicode, are encouraged for new designs.
DOS code pages are typically stored in .CPI files. [16] [17] [18] [19] [20]
These code pages are used by IBM in its AIX operating system. They emulate several character sets, namely those ones designed to be used accordingly to ISO, such as UNIX-like operating systems.
Code page 819 is identical to Latin-1, ISO/IEC 8859-1, and with slightly-modified commands, permits MS-DOS machines to use that encoding. It was used with IBM AS/400 minicomputers.
These code pages are used by IBM in its OS/2 operating system.
These code pages are used by IBM when emulating the Microsoft Windows character sets. Most of these code pages have the same number as Microsoft code pages, although they are not exactly identical. Some code pages, though, are new from IBM, not devised by Microsoft.
These code pages are used by IBM when emulating the Apple Macintosh character sets.
These code pages are used by IBM when emulating the Adobe character sets.
These code pages are used by IBM when emulating the HP character sets.
These code pages are used by IBM when emulating the DEC character sets.
These code pages are used by Microsoft in its own Windows operating system. Microsoft defined a number of code pages known as the ANSI code pages (as the first one, 1252 was based on an apocryphal ANSI draft of what became ISO 8859-1). Code page 1252 is built on ISO 8859-1 but uses the range 0x80-0x9F for extra printable characters rather than the C1 control codes from ISO 6429 mentioned by ISO 8859-1. [24] Some of the others are based in part on other parts of ISO 8859 but often rearranged to make them closer to 1252.
Microsoft recommends new applications use UTF-8 or UCS-2/UTF-16 instead of these code pages. [25]
These code pages represent DBCS character encodings for various CJK languages. In Microsoft operating systems, these are used as both the "OEM" and "Windows" code page for the applicable locale.
These code pages are used by Microsoft in its MS-DOS operating system. Microsoft refers to these as the OEM code pages because they were defined by the original equipment manufacturers who licensed MS-DOS for distribution with their hardware, not by Microsoft or a standards organization. Most of these code pages have the same number as the equivalent IBM code pages, although some are not exactly identical. [26]
These code pages are used by Microsoft when emulating the Apple Macintosh character sets.
The following code page numbers are specific to Microsoft Windows. IBM may use different numbers for these code pages. They emulate several character sets, namely those ones designed to be used accordingly to ISO,[ clarification needed ] such as UNIX-like operating systems.
HP developed a series of Symbol Sets (each with its associated Symbol Set Code) to encode either its own character sets or other vendors’ character sets. They are normally 7-bit character sets which, when moved to the higher part and associated with the ASCII character set, make up 8-bit character sets.
These code pages are independent assignments by third party vendors. Since the original IBM PC code page (number 437) was not really designed for international use, several partially compatible country or region specific variants emerged.
These code pages number assignments are not official neither by IBM, neither by Microsoft and almost none of them is referred as a usable character set by IANA. The numbers assigned to these code pages are arbitrary and may clash to registered numbers in use by IBM or Microsoft. Some of them may predate codepage switching being added in DOS 3.3.
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List of known code page assignments (incomplete):
ID | Names | Description | Origin | Platform | DOS | OS/2 | Windows | Mac | Else | Encoding | Comment |
---|---|---|---|---|---|---|---|---|---|---|---|
0 | N/A | Reserved | IBM, Microsoft | N/A | 3.3+ | 1.0+ | ? | ? | ? | Internal OS use [34] | |
437 | CP437, IBM437 | PC US | IBM [46] | IBM PC | 3.3+ | 1.0+ | Yes | ? | Yes | 8-bit SBCS | |
57344 - 61439 | N/A | Private use derivations | IBM | N/A | N/A | N/A | N/A | N/A | N/A | various | Private use code page derivations (E000h-EFFFh) |
65280 - 65533 | N/A | Private use definitions | IBM | N/A | N/A | N/A | N/A | N/A | N/A | various | Private use code page definitions (FF00h-FFFDh) |
65534 | N/A | Reserved | IBM, Microsoft | N/A | ? | ? | ? | ? | ? | various | Internal OS use (FFFEh) |
65535 | N/A | Reserved | IBM, Microsoft | N/A | 3.3+ | 1.0+ | ? | ? | ? | various | Internal OS use (FFFFh) [34] |
Many older character encodings (unlike Unicode) suffer from several problems. Some vendors insufficiently document the meaning of all code point values in their code pages, which decreases the reliability of handling textual data consistently through various computer systems. Some vendors add proprietary extensions to established code pages, to add or change certain code point values: for example, byte 0x5C in Shift JIS can represent either a back slash or a yen sign depending on the platform. Finally, in order to support several languages in a program that does not use Unicode, the code page used for each string/document needs to be stored.
Applications may also mislabel text in Windows-1252 as ISO-8859-1. The only difference between these code pages is that the code point values in the range 0x80–0x9F, used by ISO-8859-1 for control characters, are instead used as additional printable characters in Windows-1252 – notably for quotation marks, the euro sign and the trademark symbol among others. Browsers on non-Windows platforms would tend to show empty boxes or question marks for these characters, making the text hard to read. Most browsers fixed this by ignoring the character set and interpreting as Windows-1252 to look acceptable. In HTML5, treating ISO-8859-1 as Windows-1252 is even codified as a W3C standard. [47] Although browsers were typically programmed to deal with this behaviour, this was not always true of other software. Consequently, when receiving a file transfer from a Windows system, non-Windows platforms would either ignore these characters or treat them as a standard control characters and attempt to take the specified control action accordingly.
Due to Unicode's extensive documentation, vast repertoire of characters and stability policy of characters, the problems listed above are rarely a concern for Unicode. UTF-8 (which can encode over one million codepoints) has replaced the code-page method in terms of popularity on the Internet. [48] [49]
When, early in the history of personal computers, users did not find their character encoding requirements met, private or local code pages were created using terminate-and-stay-resident utilities or by re-programming BIOS EPROMs. In some cases, unofficial code page numbers were invented (e.g. CP895).
When more diverse character set support became available most of those code pages fell into disuse, with some exceptions such as the Kamenický or KEYBCS2 encoding for the Czech and Slovak alphabets. Another character set is Iran System encoding standard that was created by Iran System corporation for Persian language support. This standard was in use in Iran in DOS-based programs and after introduction of Microsoft code page 1256 this standard became obsolete. However some Windows and DOS programs using this encoding are still in use and some Windows fonts with this encoding exist.
In order to overcome such problems, the IBM Character Data Representation Architecture level 2 specifically reserves ranges of code page IDs for user-definable and private-use assignments. Whenever such code page IDs are used, the user must not assume that the same functionality and appearance can be reproduced in another system configuration or on another device or system unless the user takes care of this specifically. The code page range 57344-61439 (E000h-EFFFh) is officially reserved for user-definable code pages (or actually CCSIDs in the context of IBM CDRA), whereas the range 65280-65533 (FF00h-FFFDh) is reserved for any user-definable "private use" assignments. For example, a non-registered custom variant of code page 437 (1B5h) or 28591 (6FAF) could become 57781 (E1B5h) or 61359 (EFAFh), respectively, in order to avoid potential conflicts with other assignments and maintain the sometimes existing internal numerical logic in the assignments of the original code pages. An unregistered private code page not based on an existing code page, a device specific code page like a printer font, which just needs a logical handle to become addressable for the system, a frequently changing download font, or a code page number with a symbolic meaning in the local environment could have an assignment in the private range like 65280 (FF00h).
The code page IDs 0, 65534 (FFFEh) and 65535 (FFFFh) are reserved for internal use by operating systems such as DOS and must not be assigned to any specific code pages.
Character encoding is the process of assigning numbers to graphical characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using digital computers. The numerical values that make up a character encoding are known as "code points" and collectively comprise a "code space", a "code page", or a "character map".
Extended Binary Coded Decimal Interchange Code is an eight-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding six-bit binary-coded decimal code used with most of IBM's computer peripherals of the late 1950s and early 1960s. It is supported by various non-IBM platforms, such as Fujitsu-Siemens' BS2000/OSD, OS-IV, MSP, and MSP-EX, the SDS Sigma series, Unisys VS/9, Unisys MCP and ICL VME.
ISO/IEC 8859-1:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No. 1, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. ISO/IEC 8859-1 encodes what it refers to as "Latin alphabet no. 1", consisting of 191 characters from the Latin script. This character-encoding scheme is used throughout the Americas, Western Europe, Oceania, and much of Africa. It is the basis for some popular 8-bit character sets and the first two blocks of characters in Unicode.
ISO/IEC 8859-15:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 15: Latin alphabet No. 9, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1999. It is informally referred to as Latin-9. It is similar to ISO 8859-1, and thus also intended for “Western European” languages, but replaces some less common symbols with the euro sign and some letters that were deemed necessary: This encoding is by far most used, close to half the use, by German, though this is the least used encoding for German.
Windows-1252 or CP-1252 is a single-byte character encoding of the Latin alphabet that was used by default in Microsoft Windows for English and many Romance and Germanic languages including Spanish, Portuguese, French, and German. This character-encoding scheme is used throughout the Americas, Western Europe, Oceania, and much of Africa. Initially the same as ISO 8859-1, it began to diverge starting in Windows 2.0.
The yen and yuan sign (¥) is a currency sign used for the Japanese yen and the Chinese yuan currencies when writing in Latin scripts. This character resembles a capital letter Y with a single or double horizontal stroke. The symbol is usually placed before the value it represents, for example: ¥50, or JP¥50 and CN¥50 when disambiguation is needed. When writing in Japanese and Chinese, the Japanese kanji and Chinese character is written following the amount, for example 50円 in Japan, and 50元 or 50圆 in China.
ISO/IEC 8859-2:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 2: Latin alphabet No. 2, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. It is informally referred to as "Latin-2". It is generally intended for Central or "Eastern European" languages that are written in the Latin script. Note that ISO/IEC 8859-2 is very different from code page 852 which is also referred to as "Latin-2" in Czech and Slovak regions. Almost half the use of the encoding is for Polish, and it's the main legacy encoding for Polish, while virtually all use of it has been replaced by UTF-8.
ISO/IEC 8859-11:2001, Information technology — 8-bit single-byte coded graphic character sets — Part 11: Latin/Thai alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 2001. It is informally referred to as Latin/Thai. It is nearly identical to the national Thai standard TIS-620 (1990). The sole difference is that ISO/IEC 8859-11 allocates non-breaking space to code 0xA0, while TIS-620 leaves it undefined.
ISO/IEC 8859-8, Information technology — 8-bit single-byte coded graphic character sets — Part 8: Latin/Hebrew alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings. ISO/IEC 8859-8:1999 from 1999 represents its second and current revision, preceded by the first edition ISO/IEC 8859-8:1988 in 1988. It is informally referred to as Latin/Hebrew. ISO/IEC 8859-8 covers all the Hebrew letters, but no Hebrew vowel signs. IBM assigned code page 916 to it. This character set was also adopted by Israeli Standard SI1311:2002, with some extensions.
The pound sign is the symbol for the pound unit of sterling – the currency of the United Kingdom and its associated Crown Dependencies and British Overseas Territories and previously of Great Britain and of the Kingdom of England. The same symbol is used for other currencies called pound, such as the Egyptian and Syrian pounds. The sign may be drawn with one or two bars depending on personal preference, but the Bank of England has used the one-bar style exclusively on banknotes since 1975.
ISO/IEC 8859-4:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 4: Latin alphabet No. 4, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1988. It is informally referred to as Latin-4 or North European. It was designed to cover Estonian, Latvian, Lithuanian, Greenlandic, and Sámi. It has been largely superseded by ISO/IEC 8859-10 and Unicode. Microsoft has assigned code page 28594 a.k.a. Windows-28594 to ISO-8859-4 in Windows. IBM has assigned code page 914 to ISO 8859-4.
ISO/IEC 8859-6:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 6: Latin/Arabic alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. It is informally referred to as Latin/Arabic. It was designed to cover Arabic. Only nominal letters are encoded, no preshaped forms of the letters, so shaping processing is required for display. It does not include the extra letters needed to write most Arabic-script languages other than Arabic itself.
ISO/IEC 8859-7:2003, Information technology — 8-bit single-byte coded graphic character sets — Part 7: Latin/Greek alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. It is informally referred to as Latin/Greek. It was designed to cover the modern Greek language. The original 1987 version of the standard had the same character assignments as the Greek national standard ELOT 928, published in 1986. The table in this article shows the updated 2003 version which adds three characters. Microsoft has assigned code page 28597 a.k.a. Windows-28597 to ISO-8859-7 in Windows. IBM has assigned code page 813 to ISO 8859-7. (IBM CCSID 813 is the original encoding. CCSID 4909 adds the euro sign. CCSID 9005 further adds the drachma sign and ypogegrammeni.)
Code page 850 is a code page used under DOS operating systems in Western Europe. Depending on the country setting and system configuration, code page 850 is the primary code page and default OEM code page in many countries, including various English-speaking locales, whilst other English-speaking locales default to the hardware code page 437.
Code page 852 is a code page used under DOS to write Central European languages that use Latin script.
The currency sign¤ is a character used to denote an unspecified currency. It can be described as a circle the size of a lowercase character with four short radiating arms at 45° (NE), 135° (SE), 225° (SW) and 315° (NW). It is raised slightly above the baseline. The character is sometimes called scarab.
Several 8-bit character sets (encodings) were designed for binary representation of common Western European languages, which use the Latin alphabet, a few additional letters and ones with precomposed diacritics, some punctuation, and various symbols. These character sets also happen to support many other languages such as Malay, Swahili, and Classical Latin.
Windows code pages are sets of characters or code pages used in Microsoft Windows from the 1980s and 1990s. Windows code pages were gradually superseded when Unicode was implemented in Windows, although they are still supported both within Windows and other platforms, and still apply when Alt code shortcuts are used.
Extended ASCII is a repertoire of character encodings that include the original 96 ASCII character set, plus up to 128 additional characters. There is no formal definition of "extended ASCII", and even use of the term is sometimes criticized, because it can be mistakenly interpreted to mean that the American National Standards Institute (ANSI) had updated its ANSI X3.4-1986 standard to include more characters, or that the term identifies a single unambiguous encoding, neither of which is the case.
Several mutually incompatible versions of the Extended Binary Coded Decimal Interchange Code (EBCDIC) have been used to represent the Japanese language on computers, including variants defined by Hitachi, Fujitsu, IBM and others. Some are variable-width encodings, employing locking shift codes to switch between single-byte and double-byte modes. Unlike other EBCDIC locales, the lowercase basic Latin letters are often not preserved in their usual locations.
In addition to traditional DEC and ISO character sets, which conform to the structure and rules of ISO 2022, the VT510 supports a number of IBM PC code pages (page numbers in IBM's standard character set manual) in PCTerm mode to emulate the console terminal of industry-standard PCs.
In addition to traditional DEC and ISO character sets the VT520 supports a number of IBM PC code pages (which refer to page numbers in IBM's standard character set manual) in PCTerm mode to emulate the console terminal of industry-standard PCs.
The coded characters in this set may be used in conjunction with coded control functions selected from ISO/IEC 6429.